The mutational specificity of furazolidone in the lacI gene of Escherichia coli
The mutational specificity of the 5-nitrofuran derivative furazolidone was determined in the lacI gene of Escherichia coli. E. coli strain TC3960 (ΔuvrB, pKM101) was treated with 10 μM furazolidone, yielding an induced mutation frequency of 30 times over the spontaneous frequency. Mutations from 88 furazolidone-induced mutants were analyzed by DNA sequencing: 74 were base substitutions, 7 were frameshift mutations, 3 were tandem base substitutions, 3 were complex mutations and 1 deletion was detected. The specificity of mutation was compared to that of furylfuramide (AF2). Differences were observed in both the site specificity and the mutagenic specificity of the two 5-nitrofuran derivatives. (1) Furazolidone-induced point mutations were observed at both G:C and A:T base pairs; 93% of AF2-induced point mutations were targeted to G:C sites. (2) At G:C sites approximately equal numbers of G:C → T:A transversions and G:C → A:T transitions were induced by furazolidone; AF2-induced G:C → T:A transversions and G:C → A:T transitions 76:49. (3) There was no observable preference for particular sequences of furazolidone-induced mutations; the prominent hotspots for AF2-induced G:C → T:A transversions, G:C → A:T transitions and -(G:C) frameshifts were at 5'-TGC-3' sequences in the lacI gene. (4) Furazolidone-induced frameshifts occurred at homopolymeric sequences suggesting that the mutations arose through a strand slippage mechanism; AF2-induced frameshifts occurred at a nonreiterated G:C base pair and could be templated, through formation of a palindrome, by a sequence 110 base pairs upstream from the site of mutation. The significant differences that we observe between the two spectra do not support the notion that structurally different 5-nitrofuran derivatives might react in a similar manner with DNA to produce premutational lesions with similar characteristics.
|Keywords||DNA adduct, Furazolidone, lacI, Mutagenesis, Nitrofuran, Nitroreductase|
|Journal||Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis|
Bertenyi, K.K.A. (Katalin K. A.), & Lambert, I. (1996). The mutational specificity of furazolidone in the lacI gene of Escherichia coli. Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis, 357(1-2), 199–208. doi:10.1016/0027-5107(96)00102-9